Booster for hydraulic braking



y 4 BERTELl-STE LZER, NOW BY MARRIAGE Re. 22,349

BERTELI STELZER SHATTOC K BOOSTER FOR HYDRAULIC BRAKING SYSTEMS Original Filed Dec. 9, 1959 V w 1AM INVENTOR.

induced July13, 94s

BOOSTER FOR UNITED STATES- PATENT omen sYsrsMs mu Stelzer, now by marriage Bertell sum:

Shattock, St. Petersbur g, Fla., assignor to William Stellar. Detroit. Mich. I Original No. 2,260.492, dated October 28, 1941,- Serial No. 308,367. December 9. 1939. Application for reissue October 20, 1942, Serial No.

(Cl. 188l52) '-12 Claims.

The invention relates to hydraulic braking systems and more particularly to a power booster system for hydraulic brakes, where the booster is controlled b the hydraulic pressure produced by the master cylinder and the fluid pressure of the fluid that serves as power to actuate the booster. The invention is related to one for which I have 111cc a patent application June 27, 1939, Serial No. 281,375.

The object of the invention is to provide a power booster where the boosted pressure is in a given proportion to the primary pressure as produced by the master cylinder and to obtain this feature at the least expense in manufacture as well as installation of the power booster.

Another object is to provide novel means for controlling the power directed to the power booster, to use the primary pressure from the :master cylinder urging the admission of power to the booster, and the fluid pressure in the housing I! clamping down a diaphragm i3 re-' sponsive to the fluid pressure in chamber it of provided with a 'seal it sliding in a cylinder bore l9 which is in communication with the primary line 3 through passage 2|]. Another passage 2i ,provdes communication between line 3 and the lowpressure chamber 22 of the pressure increasing device. This is to impose the primary pressure on the secondary pressure in chamber 23- booster to oppose the admission. This results in a simplification of construction as well as a number of minor advantages which 'will become apparent in the description.

A further aim is to obtain a construction that can be used in any fluid'pressure system, using a higher pressure as a means 01' power, be it a source of air pressure from an air pump, atmos- Other features and advantages will become apparent upon inspection of the drawing, wherein:

Fig. 1 is a sectional elevation of the improved 1 booster in combination with a diagram of. the

pedal 2 b the operator to produce a primary pressure in the primary line 3 leading to the power booster which consists in its main components or a hydraulic cylinder [with a piston 5 sliding therein to serve as a pressure increasing device, a power cylinder or expansible' motor mechanism composed of a shell 5 extending, from cylinder 4, a shell I and a diaphragm 8 acting on g a diaphragm piston plate 9 secured to piston rod iii engaging said piston 5 through a shoulder or' collar ll. Another main part of the power booster is the valve mechanism which in this em- -bodiment is mounted to shell 6 and consists ot a which communicates with the conventional wheel cylinders 24 through the secondary or hydraulic brake line 25. In the "oi!" position, as illustrated in Fig. 1, piston 5 rests against recess 26, whereas piston rod ill, whose one end slides in piston 5 a short distance, limited by a stop nut 21, allows I communication between chambers 22 and 23 .through port 45 and passage 44. Piston 5 isprovided with a piston seal 28. Chamber 22 is sealed chamber filled with a wick saturated with bydraulic brake fluid or oil. A spring 3i yieldingly urges the pistons into the f'ofl" position. The

. pheric pressure against a vacuum produced by an internal combustion engine or vacuum pump, or

be it oil pressure produced by an oil pump.

valve mechanism is also shown in the oil' position. It is urged into that position by a conical spring 32 and by the valve spring I3 which seats valve 34 to shut oi! the source of power 35 consisting of a supply of fluid under pressure in communication with chamber 36 through line 81. The lower extremity of valve 34 is unseated in the ofl position so that there is communication between low pressure chamber 38 and power cylinder chamber I 4 through passage 29, through the small drilled holes in piston or plunger i'l', chamber i5, and tube It. [A hole" serves to provide communication between chamber 4i and low pressure chamber 88, which is connected with the source of low pressure 42. By low pressure I.

refer to a pressure lower than the pressure of the source of power 35. Thus, it the latter has a pressure above atmospheric, 2 may be at atmospheric pressure, and if is at atmospheric pressure, 42 may designate a source of vacuum. In the latter case, some question may arise as to what may be the source of power, however, in this description I shall consider 2! as the source of power, even though 42 may be a vacuum pump or the intake manifold of an internal combustion engine.

. In operation, assuming the hydraulic-booster in the "ofl position as shown in Fla. 1, and that" factory.

the operator depresses loot pedal 2 to actuate the master cylinder I, a primary pressure is produced in line 3 and communicated to chambers I2, 2i, 0.. and the wheel cylinders 24.. Due to the low pressure required to expand the brake shoesbe line they come into contact with the drums the pressure does not build up, the hydraulic pressure acting on piston ll' may be sui'ncient to overcome ispring 82 and thereby close oi! the .low pressure chamber II from chambers." and when the piston seats against valve (but the pressureis not sumcient to compress valve spring a to lift valve ll. Thus no power i's dlrected to the ex pansible motor mechanism. By further depression of the root pedal 2 fluid flows from. the master cylinder through line. I. passage I l chamand assuming the hydraulic pressure in the' her. 22, hole ll. and brake line II to the wheel cylinders ll, until the brake shoes begin to engage the brake drums and the resistance builds up.

Further depression or the brake pedal by the operator is accompanied by an i'ncreaseinhydraulic pressure which now overcomes spring '13 l and lifts valve N to allow fluid. under pressure ironrthesource oi power ll into chamber Ii to be directed to chamber ll of the power cylinder.

Thus the fluid acting on the diaphragm forces diaphragm piston s and with it piston rod II to--- wards the hydraulic booster cylinder whereby the shoulder ll picks up piston 5 and at the same time closes the hydraulic passage. between the primary line I and chamber 23." Thus the pressure is increased in chamber II, amounting to the primary pressure in chamber 22 plus the pressure super-imposed by'the expanslbie motor mechanism. In the meantime the fluid pressure V in chamber" acting on diaphragm is and piston rodillis oases in the. primary line is one third or the pressure in the secondary line, and neglectins the displacement of piston rod ill and the action of the varie oussprings.;then the ratio between thearea of piston 5 and the eilective area of diaphragm I;

should be twice the ratio between the area of piston i1 and the eflectivearea of diaphragm ll. thus it the eflective area of diaphragm I is I 60 tlmes thearea of piston I, the eflective area of diaphragm is must be 30 times as large as the area of piston II. It the displacement of piston to be considered. the ratio between the area oi piston rod lland piston 8 must be added to the booster ratio of the expansible motor mechanism. Using actual figures for example,

primary line to be 100 lbs. per square inch, so that 1 "the desired pressure in the wheel cylinders is 800 lbs. per square inch, and assuming that piston I has 1 square inch and rod it an area oi .1 square inch, then the pressure imposed by the primary pressure on the secondary pressure is 90 lbs., the booster ratio is 2.1, and the proportion between the eflective area of diaphragm I and piston i, 2.1 times as-great as the proportion be tween the eflective areaoi diaphragm II and piston l'l'. Thus assuming that diaphragm I plate I! has been opposing the hydraulic piston under pressure commensurate with the exertion on the iootpedal! and primary pressure. The positioned! the valve mechanism when admittins power" is shown in Fig. 2'. The excursion is limited by'smali projections ll so that the fluid can stillqpass.

' i In the holdingposition, where the exertion on the foot pedal ishel'ther decreased nor increased. the valve :4 is seated not. only against the'seat in the piston ,I'I' but also the seat in housing I2.

I shutting on *the low pressure as well as the high pressure from source".

Supposing now that the operatorrelease's his foot from the brake pedal to release the brakes.

the resulting tall in the primary pressure causes plstomll' to yield to the fluid pressure in cham-' ber ll, whereby valve 84 unseats itself from pis- II' so as to let in only a certain amount of 'fluid ton i1 and allows the fluid in chambers is and- II to escape into chamber II and from thereto the source of low-pressure l2. This relieves the Y pressure'on; piston s, and spring sl returns it to the "on" position, unseatin'g collar again from piston l to allow the brake shoes to contract completely and return the hydraulic fluid to the master cylinder. a

' It is impo t and desirable to 'malntain ap f proximately the same booster ratio during the application or the brakes to give the operator the fieel" of the brakes and at the same timeto be economical with the expenditure or power. "I

have found that, certain types, of vehicles a booster ratio of not more than 1:2, whereasin others where the weight is greater and the brakes are; larger a booster ratio oi 1:4 is more satists; a booster is'tb be constructed st p: 'a boo er ra s! lzlliwhere-the pressure discriminate between V has 60 square inches, and piston i1 .42 square inch, the required area 01' diaphragm I! would be 60X 12 square inches Due to the springs and internal resistance the booster ratio is somewhat lower. When the maximum power is reached where there is no more reserve the overall booster ratio does not increase.

any further. but drops oft; with increased pedal pressure.'=

In order not to encumber the drawing, the booster mechanism has been-illustrated in the position shown. but it is apparent that it may be a mounted in a vehicle with the hydraulic cylinder at the top, or 'in any other position as long as bleeding does not become too diflicult. Since there are no other than plpe connections,.the

booster unit may be placed or mounted at any convenient place in the vehicle. I W I wish to make it clearly understood, that by the term .boosterf I mean to designate a device which serves to boost or increase the hydraulic is in operations -i While onelllustratlve embodiment has been shown, it is apparent that thelnvention' maybe carried out in many ways diflerent i'romthat shown. and therei'oreldo not ,wish to be limited v in the application or in the construction to the particular embodiment except as by the scope or the appended claims.

i I claim: I

1 1,1 a hydraulic braking y em having 5 master cylinder toproduce a primary pressure, andv wheel cylinders to be actuated. by a secondary pressure. .a fluid pressure line connected to the master cylinder, and a fluid pressure line connected to the wheelcylinders, a pressure booster comprising} pressure increasing device having a primaryepressure side communicating with the flrst named fluid pressure line and .pressure is higher than said primary pressure,

control valve means for said motor, means responsive to said primary pressure to actuate said control valve means to connect said motor to a source of pressure diii'erential, and means directly responsive to diflerentlal pressures in opposite ends-t said motor to oppose said last named means, to tend to reduce differential pressures in said motor, said pressure booster forming a self-contained unitwholly separate from the master cylinder and the wheel cylinders and connected thereto solely by said fluid pressure lines, said pressure booster being so constructed as to ailord communication between said secondary pressure side and said primary pressure side when pressure in the latter is higher than 'in said secondary pressure side.

2. In a hydraulic braking system having a master'cylinder for producing a primary pressure, wheel cylinders to be actuated by a secondary pressure, a fluid pressure line connected to the master cylinder, and a fluid pressure line connected'to the wheel cylinders, a pressure booster comprising a pressure increasing device having a primary pressure side communicating with the first named fluid pressure line and a secondary pressure side communicating with the second named fluid pressure line, an expansible motor for actuating the pressure increasing device, said pressure booster being constructed and arranged ior utilizing said primary pressure to assist said motor in increasing said secondary pressure while the latter is higher than said primary pressure, valve means for controlling pressures in said motor, pressure sensitive means responsive to said primary pressure to actuate said valve means to connect said motor to a source of pressure diflerential, pressure sensitive means comprising a diaphragm directly responsive to diflerential pressures in opposite ends of said motor to oppose said last named means, to

' tend to reduce differential pressures in said motor,

said two opposing pressure sensitive means being proportioned to produce an increase in said secondary pressure which is proportional to the primary pressure in a predetermined ratio, and means yieldingly urging said valve means to a motor-deenergizing position, said pressure booster forming a single self-contained unit separate from themaster cylinder and the wheel cylinders and connected thereto solely by said fluid pressure lines, said pressure booster being so constructed as to aflord communication between said secondary pressure side and said'primary pressure side when pressure in the latter is higher than in said secondary pressure side.

3. In a hydraulic braking system having a master cylinder for producing a primary pressure,

and wheel cylinders to be actuated by secondary pressure, a pressure booster comprising a booster cylinder one end 01' which is a primary pressure chamber communicating with the master cylinaasco and said piston being constructed to cooperate with 'each other to aflord communication be-' tween said chambers when said motor is deenergized and to close such communication when said motor is energized, the communication be .tween said chambers when said motor is deenergized being such as to ,aflord relatively unimpeded flow of hydraulic fluid from one of said chambers to the other, said rod and said'piston 'being so constructed and arranged that said rod pressure chamber communicating with the master cylinder and the other end of which is a secondary pressure chamber communicating with the wheel cylinders, a piston in said booster cylinder, a difl'erential fluid pressure motor having a pressure responsive unit including a rod axitween said chambers when said motor is deennr'zizcd, said communication being such as to afford relatively unimpeded flow of hydraulic fluid from one of said chambers to the other.

said rod portion, when in engagementwith said piston, 'closing communication between said chambers, and a control valve mechanism for said motor operative for controlling differential pressures in said motor to eilect movement oi saidpiston to generate a secondary pressure substantlally proportional to the primary pressure.

5. In a hydraulic braking system having a master cylinder for producing a primary pressure, and wheel cylinders to be actuated by a secondary pressure. a pressure booster comprising a booster cylinder one end of which is a primary pressure chamber communicating with the mastercylinder and the other end 'of which is a secondarv pressure chamber communicating with the wheel cylinders, a piston in said boostat cylinder, a diflerential fluid pressure motor having a pressure responsive unit including a 'rod axially movable in axial alignment with said piston. said rod having a portion engageable with said piston to move the latter toward the second named 'end oi said booster cylinder upon enereizat on 01' said motor, said piston and said rod being constructed to cooperate with each.

other to ,aflord communication between said chambers when said motor is deenergized, said one of said chambers to the other, said rod portion, when in engagement with said piston,

der and the other end 01' which isa secondary pressure chamber communicating with the wheel cylinderspa piston in said booster cylinder, a motor having a power responsive unit including a rod axially aligned with said piston, said rod closing communication between said chambers, and a control valve mechanism. for said motor constructed and arranged to, be responsive to said primary pressure and to the fluid pressure aflecting said motor whereby energization of said motor eflects movement of said piston to generate a. secondary pressure proportional to the primary pressure.

6. In ahydraulic braking system having a cylinder for producing a pressure, and wheelcylinders to be actuated by a secondary pressure, apressure booster comprising a booster cylinder one end-oi whichis a primary pressure I chamber communicating with the master cylinder and the other end oi which is a secondary pres- -sure.chamber communicating with the wheel cylinders, aplstonin saidbooster. cylinder, a diiierential fluid pressure motor having a pressure reispon'sive unit including'a rod axially movable in aagsaa t s booster cylinder upon operation oi the master cylinder wiilact against the corresponding end a or said pistonto assistsaid motor in moving said piston, and aoontrol valve mechanism for said motor comprising a piston elem phragm element subject to diflerential pressures axial alignmentwith said piston, said 'rod having,

a portion engageable with said piston, to move the latter toward the second named end of said booster cylinder uponenergization of said motor.

said piston and said ,rod being constructed to afford communication'between said chambers when saidmotor is deenergizedsaid rod portion, when in engagementwith said piston. closin communication between said chambers: and a" control valve mechanism for said motornormally operative ior'balancingpressures therein, said valve mechanism comprising a pressure sensitive in said motor.

9. In a hydraulic brakingsystem having a master cylinder to produce a primary pressure; and

wheel cylinders to be actuated by a secondary pressure, a pressure booster comprising a diflerential fluid pressure motor having a pressure responsive unit including an axialrod, a booster cylinder rigidly. carried by said motor axially thereof and into one end of which said rod extends, a pistonflmounted in said booster cylinder and, having lost motion connection with said rod.

' said end of said'booster cylinder communicating element responsive tosaid primary pressure for.

' closing communication between the'ends-oi said motor andv connecting one end'oi said motor to a source of pressure differential to effect actuation of said piston to increase the secondary preswith the master cylinder, the other end oi said u booster cylinder being a'pressure chamber and communicating with the wheel cylinders, said rod and said piston-belngconstructed and arranged with respect to each other to afford communication between the endso! said booster cylinder when said motor is deenergized, and to close such, communication when the motor is enersure, and a diaphragm device responsive to diflerential pressures in said motor for opposing movementor said pressure sensitive element. '7. In; a hydraulic braking system having master cylinder to produce a primary pressure,

and wheel cylinders to be actuated by a secondary v pressure, a pressure booster comprising a diflerential fluid pressure motor having apressure responsive unit'including an axial rod, a booster cylinder rigidly carried by said motor axially thereof and into one end of which said rod extends, a piston mounted in said booster cylinder and having lost motion connection with said rod,

said end of said booster cylinder communicatin with the master cylinder, the other end oi said booster cylinder being a pressure chamber and communicatingjwith the wheel cylinders, said rod and said piston being constructed and arranged with respect to each other to aflord communication between theends of saidbooster cylinder: when said motor is deenergin'ed, and to close such communication when the motor is energized whereby fluid entering the first named end 01 saidbooster cylinder uponoperation oi the master cylinder will" act against the corresponding end or said piston to" assist said motor in movin said piston, and a control valve, mechanism for controlling the energization of said motor. 8. In a hydraulic braking system having a master cylinder. to produce a primary pressure, a

and wheel cylindersto be actuated by a secondary pressure, a pressureboofler comprising adifl'erential fluid pressure motor having a prcssure're- Sized whereby fluid entering the first named end or said booster cylinder upon-operation oi the master cylinder will act against the correspond.- ing end of said piston to assist said motor inmoving said 'piston, and a control valve mechanism for said motor comprisin a valve piston ,mounted, in said motor, said motor being proi vided with a fluidpassage through which said valve piston is subjected to master cylinder pressures'to be .movedto connect said motor'to a source of pressure differential, a diaphragm hous- 'ing .carried by, said motor, and a diaphragm in said housing connected to said valve piston and "subject to differential pressures aflecting said .motor to oppose such movement or said valve piston.

10. In a hydraulic braking system having a master cylinder to produce a primary pressure, and wheel cylinders to be actuated by a secondary pressure, a pressure booster comprising a differential fluid pressure motor havin a pres- I sure responsive unit including an axial rod, a

booster cylinder rigidly carried by said motor axially thereof and into oneend of which said rod extends, a' piston mounted in said boostercylinder and having lost motion connection with sponsiveunit including an axial a booster cylinder rigidly carried by said motor axially thereof and into one end oi which said rod ex-jtends, apiston mounted in said booster cylinder and having lost motion connection with said rod;

said'end of said booster cylinder communicating with the mastercylinder, the other end of said said rod, saidend oi saidJbooster cylinder com- I municating with. the master cylinder. the'other end of said booster cylinder'being a pressure chamber and communicating with thewheei cylinders, said rod and said piston being constructed and arranged with respect to each other to afford communication between the ends 0! said booster cylinder when said motor is deenergized', and to close such communication when thelmotor "is energized whereby fluid entering the first, named booster cylinder being a pressure chamber and communicating "with the wheel cylinders, said rod and said piston being constructed and arran'ged with respect to each other to aiiord communication between the ends of -sald booster-cylinder close communication between the ends of said when said motor is deenergized, and to close such whereby moo entering the ilrst-named end of said oommunication when is energized end or said booster cylinder uponoperation of the master-cylinder will actsagainst the corre-- spending end or said piston to assistsaidmotor in moving said piston, and a control valve mechanism tor saidflmotor comprising a valve normally positioned to connect theends of said motor to eachother to balance pressures therein 4 andqoperable by master cylinder pressures to motor, a' valve element normally in closed posi-"" tion and movable by said valve piston to open positionto connect one end of said motor to a t subiect t master cylinder pressures, and an opposing diabooster comprising a pressure increasing device source of pressure differential to operate said piston, and a diaphragm subject to pressures in the ends of said motor and operable when said end of said motor is connected to said source to oppose movement of said valve piston from normal position.

11. In a hydraulic braking system having a v master cylinder operated by the operator to produce a primary pressure, and wheel cylinders to be actuated by a secondary pressure, a pressure booster comprising a pressure increasing device having a primary pressure side in communication with said master cylinder and a secondary pres sure side in communication withsaid wheel cylinders, an expansible motor to actuate said pressure increasing device to increase the secondary pressure, said booster being so constructed and arranged that said primary pressure performs part of the workto apply the brakes, a source of pressure for operating said motor, valve means to control differential pressures in said motor and normally connecting the ends of said motor to each other, hydraulic pressure sensitive means responsive to said primary pressure to actuate said valve means to first disconnect the ends of said motor from each other and then connect one end of said motor to said source, fluid pressure sensitive means having opposite sides responsive to pressures in the respective ends of the motor and arranged to oppose said last named means,

to tend to disconnect said end of said motor from said source and then connect it to the other end of said motor to balance pressures in said-motor, and means yieldingly urging said booster to its ofi" position .12. In a hydraulic braking system having a master cylinder operated by the operator to pro- I duce a primary pressure, and wheel cylinders to be actuated by a secondary pressure, a pressure having a primary pressure side in communication 'with said master cylinder and a secondarypressure side in communication with said wheel cylinders, an expansible motor to actuate said pressure increasing device to increase the secondary pressure, said booster being so constructed and arranged that said primary. pressure performspart of the work to increase said secondary pressure, a source of fluid pressure, valve means to control differential pressures in said motor and normally connecting the ends of said motor to each other, hydraulic pressure sensitive means responsive to said primary pressure to actuate said valve means to disconnect the ends of said motor from each other and connect one end of said motor to said source, diaphragm type fluid pressure sensitive means responsive to the pressures in the respective ends 01" said motor and arranged to oppose said last named means/to tend to reduce the power of said motor and to thereby tend to decrease the booster action with a consequent decrease in the secondary pressure, said two opposing pressure sensitive means being proportioned to produce a predetermined proporcontained unit, connected with the rest of the braking system by fluid pressure lines. BERTELI STELZER SHATIOCK,

Berteli Stelzer, now by marriage Berteli Stelzer Shattock. 

